Minimally invasive vessel harvesting has gained widespread acceptance in the field of surgery as a method for obtaining graft vessels for coronary artery bypass graft (CABG) procedures. When using such a method, for example, a long portion of the saphenous vein is removed from a patient's leg, operating through only one or a small number of short incisions in the leg. The vein is then segmented according to the number and type of grafts needed for the CABG procedure.
A surgical technique for the removal of a vessel such as a saphenous vein is disclosed in U.S. Pat. No. Re. 36, 043 issued to Knighton on Jan. 12, 1999 (hereinafter, Knighton). In this procedure, the surgeon uses an endoscope having a lumen through it. A grasping instrument is inserted in the lumen in order to grasp the saphenous vein, which is then withdrawn into the lumen of the endoscope. The endoscope is maneuvered along the length of the vein while side branches of the vein are ligated and transected whenever encountered. Although this surgical method provides for a minimally invasive technique, there are several drawbacks associated with it. First, in practicing this method, there is limited visibility of the saphenous vein and its side branches because viewing is limited to the immediate area directly in front of the endoscope. Second, the illumination within the subcutaneous space created by this type of endoscope is also limited to the light emitted directly at the distal portion of the endoscope. A third drawback to the described method is that the side branches of the saphenous vein limit the maneuverability of the endoscope. This limited maneuverability is because the outer edge of the endoscope body is prevented from advancing along the trunk of the saphenous vein until the encountered side branches are ligated and transected. Once free, the endoscope is then maneuvered until the next side branch is encountered. Moreover, it has been found that methods that use this type of endoscope (having a lumen) provide a restricted working space because the sidewalls of the endoscope body confine the working instrumentation to a limited area. A fourth drawback to the vessel harvesting method described in Knighton is that it requires a "threehanded" approach. One hand is required to hold and maintain the endoscope in position, a second hand is required to hold the free end of the transected vessel with a grasper, and a third hand (of an assistant) is required to dissect connective tissue away from the vessel.
Ethicon Endo-Surgery, Inc., Cincinnati, Ohio, has developed and promoted two very successful devices and an associated method for endoscopically harvesting blood vessels such as the saphenous vein. In this method, a surgeon (or surgical assistant) uses an optical tissue dissector known as the ENDOPATH SUBCU-DISSECTOR optical dissector for separating subcutaneous tissue away from the saphenous vein. Then the surgeon or assistant uses an optical retractor known as the ENDOPATH SUBCU-RETRACTOR optical retractor for retracting the dissected tissue away from the saphenous vein. Both of these devices have a transparent, concave working head having a spoon shape. The optical retractor has a larger, working head, however, than the optical dissector. The concave, working head defines a working space for the end effectors of an instrument such as a grasper, a scissors, or a clip applier. The optical dissector and optical retractor allow the surgeon to see the tissue on which is operated. These devices (hereinafter, Knight devices, Knight optical dissector, Knight optical retractor) and a surgical method for their use have been issued to Knight, et al, and are disclosed in U.S. Pat. No. 5,667,480 issued on Sep. 16, 1997 and in U.S. Pat. No. 5,722,934 issued on Mar. 3, 1998, both of which are hereby incorporated herein by reference.
The Knight optical dissector and retractor are each used with a thirty-degree endoscope in which the viewing angle of the distal end of the scope is slanted 30 degrees from the longitudinal axis of the instrument. The field of view is therefore directed ahead and to one side of the axis. This type of endoscope is ideal for use with the spoon shaped heads of the Knight devices because the surgeon desires to view the tissue directly ahead of the head and beneath the opening of the head where the tissue may be operated on.
In U.S. Pat. No. 5,902,315 issued to DuBois on May 11, 1999, and which is hereby incorporated herein for reference, a device (hereinafter, DuBois device) is described for dissecting and retracting a blood vessel from subcutaneous tissue. The DuBois device is similar to either of the Knight devices, and has the addition of a fluid carrying system for purging particulate matter from the working space of the concave head of either the optical dissector or optical retractor. A fluid flow (of carbon dioxide gas, for example) is used to purge smoke and/or mist from the enclosed working space in order to maintain visualization of the tissue being operated on. Particulate matter accumulates due to the use of electrosurgical or ultrasonic cutting devices, whereas condensation of moisture in the working space occurs due to the temperature differential between the inside and outside of the patient's body.
The Knight and DuBois devices and methods for their use for harvesting vessels represent a significant advance in the surgical art. Nevertheless, widespread use of these devices and methods has helped to clarify even more the needs of the surgeon for harvesting blood vessels. For example, for some surgeons or physician assistants, the repeated application of force required to advance the concave head of the Knight optical dissector in order to separate tissue from the vein can become physically tiring. This is especially true when harvesting a long (over 18 inches) portion of vein such as would be needed for a multiple CABG procedure. For these surgeons/assistants, the time required to dissect the vein can be several minutes longer than the time required by others who are better able to exert the manual dissection force required during the procedure. What is needed, therefore, is a device and method to reduce the initial dissection force required for separating the vein from surrounding tissue. Then the Knight or Dubois devices having the necessary concave heads for creating a working space could be inserted into the tissue more easily than before. Furthermore, the initial dissecting device and method should be used with the same, thirty-degree endoscope as is needed for the Knight devices to minimize the amount (and cost) of visualization equipment needed in the operating room.
In recent years, a number of penetrating optical instruments, sometimes referred to as optical trocars, have been developed for gaining access into a cavity in the surgical patient. One of the earliest examples is disclosed in U.S. Pat. No. 5,271,380 issued on Dec. 21, 1993 to Riek, et al. This penetration instrument has a hollow shaft for receiving an endoscope, and a transparent, conical distal end. Other examples of optical, penetration instruments are disclosed in the following U.S. Patents: U.S. Pat. No. 5,380,291 issued on Jan. 10, 1995 to Kaali; U.S. Pat. No. 5,441,041 issued on Aug. 15, 1995 to Sauer, et al; U.S. Pat. No. 5,423,848 issued on Jun. 13, 1995 to Washizuka. All of these patents describe instruments having transparent, conical tips, or the equivalent. In U.S. Pat. No. 5,569, 291 issued on Oct. 29, 1996 to Privitera, et al, a conical-tipped optical trocar is also disclosed. It is suggested that this surgical instrument may be used in "tunneling techniques to provide access to a desired surgical site remote from the point of entry" in connection with saphenous vein harvesting (see col. 4, line 43-44.)
In all of the references for optical, penetrating instruments cited in the present disclosure, the apex, or distal-most portion of the conical-shaped tip, lies on the central longitudinal axis of the instrument. These types of instruments are intended for use primarily with a zero-degree endoscope in which the field of view is directly ahead of the distal end of the endoscope. When the zero-degree endoscope is inserted into the optical, penetrating instrument, the apex is centered in the field of view, and it is possible to view images all around the apex within the field of view. If any of these conical-tipped instruments were to be used with a thirty-degree endoscope, the apex of the conical tip would be off-center of the field of view, and only images appearing on one side of the conical tip could be visualized. This would present a problem to the surgeon if such an arrangement were being used to "tunnel" along a blood vessel. Only one side or the other of the conical tip could be used as a window to see tissue. If the blood vessel being dissected from tissue happened to be on the "blind side" of the tip, then the surgeon, for example, may not be able to see side branches of the vessel as they are encountered. If side branches are "skipped" and not ligated and severed cleanly from the main trunk of the blood vessel, there would be significant danger of tearing side branches during the dissection of more distal portions of the blood vessel. It is clearly advantageous to be able to visualize all tissue adjacent to the optical penetrating tip. What is needed, therefore is an surgical instrument and method, which can be used as an initial dissection or "tunneling" instrument for vessel harvesting in combination with a thirty-degree endoscope. The surgical instrument, furthermore, should have an optical penetrating tip that allows visualization of all tissue adjacent to the optical penetrating tip.